Answer:
There are two main types of stem cells: embryonic stem cells and adult stem cells.Stem cells provide new cells for the body as it grows, and replace specialised cells that are damaged or lost. They can divide over and over again to produce new cells.
I hope this counts - cell wall! helps keep most materials out but allows specific materials to pass through. animal cells do not have a cell wall
Answer:
D. There is no enough oxygen in the culture fluid
Explanation:
The cells in the test tube need to carryout one of the important metabolic processes of living organisms - respiration. The process involves the breakdown of glucose to generate energy for other metabolic processes in the cell.
Respiration can be carried out in the presence of oxygen (aerobic) or in the absence of oxygen (anaerobic). Human cells are primarily aerobic but can carryout respiration anaerobically in the presence of inadequate oxygen.
For aerobic respiration, glucose is broken down in the presence of oxygen to produce carbon-dioxide, water and energy in the form of ATP:

<em>In the absence of oxygen, the glucose becomes converted to lactic acid and a smaller amount of ATP is produced as compared to aerobic respiration.</em>
<em>Hence, lactic acid gradually builds up in the absence of oxygen due to anaerobic respiration.</em>
The correct option is D.
Answer:
D. hotter rock rises and cooler rock sinks.
Explanation:
We know that as we move <u>towards Earth's center</u>, the <u>temperature rises</u>. This rise in temperature causes rocks to melt (magma). The high temperature and melting of rocks <u>decrease the density of material </u>which makes it <u>move upward</u>. By <u>moving upward</u>, the molten rock <u>starts turning solid</u> and becomes <u>denser again</u>. Here, it <u>sinks back due to gravity</u>. This upward and downward movement of rocks due to density and temperature makes a convection cell.
PS: The formation of convection cells in Earth's interior is also the reason for plate tectonics.
I believe the order is...
Producers
Primary Consumers
Secondary Consumers
Tertiary Consumers
I hope this helps!